Driven by global carbon reduction targets, China has been gradually transitioning toward the development of clean, green, and low-carbon energy. Abandoned mines are endowed with abundant geothermal resources, with their underground tunnel water storage systems providing a natural conduit for geothermal production and injection. This study focuses on the −410 m tunnel of a Jining coal mine. Based on fluid flow and heat transfer theory within underground tunnels, and incorporating engineering parameters, a coupled multi-physics numerical model for production and injection wells was developed. Seven simulated operating conditions were modeled across two categories: single-season cooling operation and dual-season winter–summer operation. These examined temperature field variations under different extraction/injection rates and operating modes, analyzing thermal breakthrough phenomena, cooling/heating potential, and long-term stability. Results indicate that under single-season cooling with constant-temperature reinjection, increased production/injection volumes significantly shorten thermal breakthrough onset times. While single-season cooling with constant-temperature-difference reinjection can satisfy building cooling demands, prolonged operation leads to sustained temperature increases, shortening system lifespan. The dual-season operation mode offered superior long-term sustainability and economic viability compared to single-season modes. Due to the inclined roadway connection between production and reinjection wells, reinjected water tends to flow along the shortest roadway, resulting in inadequate utilization of roadway storage capacity. The study proposes increasing the geothermal water circulation distance between these wells to extend rock-water heat exchange duration. These findings provide critical technical support and theoretical reference for the construction and operation of geothermal projects in abandoned coal mines.
Zhang et al. (Sun,) studied this question.